


Something New

by FullOfBoredom



Series: Crossmare [2]
Category: Undertale (Video Game)
Genre: Creampie, Crossmare - Freeform, Dom/sub Undertones, Established Relationship, M/M, Mirror Sex
Language: English
Status: Completed
Published: 2021-01-31
Updated: 2021-01-31
Packaged: 2021-03-17 17:40:32
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 2,638
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29104194
Author URL: https://archiveofourown.org/users/FullOfBoredom/pseuds/FullOfBoredom
Summary: Mirrors are windows to the soul. Cross wants an eyeful.Sequel to Fool Me Thrice, but not necessarily required to read. Is mostly PWP.
Relationships: Sans/Sans (Undertale)
Series: Crossmare [2]
Series URL: https://archiveofourown.org/series/2135421
Comments: 10
Kudos: 115





	Something New

“You summoned me Cross?” Nightmare walked into the throne room, said skeleton already in his seat with a serious face that his blush betrayed. One leg crossed over his lap, his eyes dragged down Nightmare’s body appreciatively. His tentacles closed and locked the door behind him with a raised brow.

“I did. I-I…” Cross shook his head and cleared his throat. He started again, hesitance gone. “I wanted to try something new.”

Nightmare stopped in front of Cross, still only eye to eye with Cross’s superior height even when seated. He took a deep breath in and removed his hands from their pockets. Even after a few of these ‘sessions,’ Nightmare’s anxiety didn’t dip until much later, tense while his mind was sharp.

“What did you have in mind?” Cross stood up to kiss him, soft and chaste. Night’s eye slid shut, lingering desire making him lean forward to kiss Cross again. Brief, but it made Cross chuckle.

“Someone’s excited.” He whispered it to Night’s ear. “It’s a surprise. I won’t remove any clothing until you fully agree to it though, I promise.” He rubbed their cheeks together, tapping Night’s forehead with his own.

“Now, sit down while I set this up, and no peeking.”

Cross’s hands led him to his throne, seating him delicately with a kiss on his fingers. Night could feel his presence nearby, moving something quietly from behind the throne somewhere, and returning quicker than expected. The drop onto the floor was heavy, then the sound of fabric tossed off to the side. 

After Cross settled the surprise, he grabbed Night’s waist to pick him up. He spun them to seat Nightmare on his lap, hands quickly pulling Night's pelvis against his, mouth nipping through his sweater at the ever present marks Cross left across his collarbone.

“Turn around for me.” Cross didn’t make them questions anymore. Instead, he spoke with pleased sighs, like Nightmare obeying commands was as delectable as it was inevitable, which, to his credit, he'd yet to be proven otherwise. The temptation to disobey never superseded the pleasure Cross would give him in exchange for handing over his inhibitions. Night flipped himself around, still unwilling to open his eyes. 

“What should I summon Cross?” Hands rested across his chest already; Cross’s favorite spots were easy to read. Night’s panting gradually got louder under Cross’s nibbling.

“You know what I like Boss, but first...open your eye.”

Night opened it slowly, focusing in on what he was facing.

A mirror.

His legs bracketed Cross’s legs, perched to stare at the reflection of himself, flushed cyan with Cross’s eyes trained on his face and hands rubbing soothingly on his thighs before kissing at Night’s neck. Night could see exactly where Cross’s gaze was lingering; mostly on his face, but his chest attracted a lot of attention even unsummoned apparently.

“Is this okay?” Cross picked at the hem of Night’s sweater. His tentacles curled around Cross’s torso firmly, turning away from the sight.

“I’m...hesitant.”

“You aren’t being forced. I can put it away.” Cross hadn’t made any move to do so, stroking along Night’s sides and kissing his shoulders with half lidded eyes. “Tell me what you specifically don’t like. I want to know what to avoid for next time.” Night’s body shook in his arms, pointedly ignoring his own reflection.

“I’m not fond of looking at myself.” Cross’s brows furrowed, meeting Night’s eye in the mirror.

“Why not? You’re so attractive.” A finger traced up his femur, making Night chirp with a surprised shiver. 

“I’m...not.” He kept his eye closed this time, sighing while Cross’s other hand followed a similar path. 

“Are you calling me a liar Boss?” Cross pushed his lap down to grind up into it. Night’s head fell back. “I told you I want you.” He wasn’t prepared for Cross’s voice by his ear. “Do you trust me?"

" _ Yes." _ Instantaneous. 

"Then let me take care of you." He took Night's trembling hands into his own. He purred against his back, comforting and soft in his gaze and ministrations. "Tell me the safe word."

"Void." His tentacles squeezed tighter. Cross didn't have a shred of worry, only hope and fondness pulsing from his soul.

"Thank you." 

Nightmare shuddered at the warmth, letting Cross's hands drop and feeling them instantly gravitate towards his sternum. He kept his eye off the mirror and summoned his breasts under Cross's waiting fingers, feeling him cup and massage them over his sweater, chin hooked over his shoulder to get a good view of the mirror and to irritate the stinging bites there.

"I wanted to see every expression you make and dedicate it to memory." Cross spoke sweetly, thumbs stimulating his inverted nippers to coax them out. "I already did that with all of your moans." He said it with purple cheeks. Night could feel his arousal against his sacrum. "I won't take your clothes off, just like I promised, but I'm gunna work you up enough to see some of those cute expressions."

"AHhh!" He'd slid under the clothes and pinched his pert buds while Night was distracted. It technically kept his promise. When Night's eye snapped open with the whine, he caught a glimpse of the view in the mirror.

His own flushed cyan face, eyes watering, tongue lax in his mouth, his full ecto glowing from beneath its cotton confines, rucked up at the hem to show off his soft stomach with Cross's wandering hands inside, pressed fully against the purple line of Cross's cock through their shorts, his face being taken in by those hungry mismatched eyelights. Exposed and embarrassed, he could only watch as one of the hands from his chest snuck into his pants.

"C-Cross!" 

"You're so wet already." He worked two fingers down through Night's slick folds, running over his clit in time with a pinch of his nipple. Cross kept up the attention, almost missing the look on Night’s face.

"So disgusting…" Night's watery eye escalated to tears, turning away in shame even as he writhed in pleasure. Cross's skull nudged his, turning them both to face the mirror.

"Look at me Nightmare." 

Night met his stare, shaking against his skull where they were pressed together. Cross smiled, easing up on his boob and switching off his clit to spread his still clothed entrance apart. It didn't let the tension lull but left head space to hear what Cross wanted to say.

"I've been looking at you this whole time. Feel that?" He knocked up against Night's ecto through all the layers. 

"But it's all so…" He whimpered in place of answering. His humiliation wrote itself in his wince, the stiffness of his splayed legs around Cross's. Cross ran his teeth over Night's delicate neck.

"So unbelievably hot." 

His fingers massaged against his lower lips, Night rocking with it while he shivered. He swallowed hard then removed Cross's hand from its resting place between his breasts.

With a twist, he pulled his sweater off.

"That's more like you." Cross chuckled into his back, drawing feather light circles across Night's sides. "Strong and confident." He trailed kisses along one of the tentacles still gripping him. "Use these extra hands of yours to make us match?" 

They made quick work of the jacket and shirt. Cross hooked into the waistband of Night's pants.

"I want to see all of you." He locked eyes with Night, prompting him to readjust before slowly removing them. He broke off to watch inch after inch, licking his teeth when his soaked cyan pussy was unveiled. "Boss, you're gorgeous."

"You're handsome too." He looked away embarrassed, but relaxed into the hug around his midsection. Cross had made it back to his eyes, a confident smile across his teeth.

"Don't hold back your reactions, ok? I'll take care of you." 

Nightmare watched Cross's agonizingly slow descent, anticipation building as he trailed lower, crying out at that first touch to his bare pussy, Cross pressing in two fingers as he watched Night be hypnotized by his hand. 

Night squirmed in his lap, able to watch Cross scissor him open, twisting and thrusting in turns, but still unable to change his own reactions. Nothing lessened by knowing, Night’s own hands gained a mind of their own.

“ _ Stars _ Nightmare.” Cross’s breath fell heavily against his back. He’d devolved to open mouth staring as Night teased his own breasts while he ground down on Cross’s fingers.

“Hnnnnngh, C-Cross!” His entire skull flushed cyan, keeping his eye laser focused on Cross’s face to block out the anxiety threatening to crash in. The brink of worry was almost past, already fading on every third grind, body trusting in the scent and aura of Cross’s soul to protect him. He heard the clink of Cross’s jaw and then his voice in his ear, dropped two octaves.

“Sit up a little. I’ll give you something better to ride on.”

He pulled his fingers free (and oh stars, he could see Cross licking them clean, hearing the wet sucking behind his head) and forced his shorts off under the clearance of Night’s impromptu lap dance. That also left Cross’s cock unhindered. It stood up tall, slotting perfectly between Night’s open folds, making them both hiss in satisfaction. Night’s first slide across the shaft had Cross seeing stars.

“It’s so-!” It was hot and rock solid against his ecto, his freshly stretched hole already aching at the thought of that first catch. Cross caught his hips when the tip finally lined up just right.

“ _ Booossss _ .” Sing song. Night broke from the stupor to focus on Cross’s heat hazed face.

“Watch it happen Nightmare.” 

His eye went to the mirror, its reflection reminding him of his current position. Seeing the smudge of color right at the barrier of his pelvic inlet, purple shining through his lighter cyan, he tightened reflexively around Cross. His weight dropped down with Cross’s guiding hands and got to SEE his body get wrecked, painting a long thick line of lavender directly up into his ectobody paired with the burn of making room for Cross. By the time he was seated, he’d been screaming out moans of overstimulation.

“Holy fuck.” Night barely heard, thoughts erased, eyes rolled back into his skull while he drooled haphazardly. His knees tried to knock together, held apart by Cross’s strong thighs. Night dropped his hands to them and leaned forward.

Then he slammed himself back.

“C-CR-ROOO-OOOOOSS!” He’d hit own sensitive spots with ease, fucking himself on Cross’s lap with guiding hands on his hips. Once he hit his stride, he turned his face to the mirror, pleading at Cross to not stop, never stop, fuck him, stars, stars, STARS!

Cross rode the wave with Nightmare. He’d lost control but he’d be a fool to be upset about his lover vigorously fucking himself apart on his cock, begging him to keep going like he had any say in the overwhelming pace. It took every single lesson in self control to not cum right then. Night’s tight cunt gripped around him, those sinful words he screamed to the heavens, the delectable faces of utter debauchery, he’d been given every temptation at once. The biggest tipping point ended up being his boobs bouncing along with him, the entire picture topped with those lovely handfuls making him growl with need.

He pulled Nightmare back with a firm grasp of his breasts, pinching and tweaking to set a new upright pace. It worked twofold to gain back control and to get a better view of Nightmare’s whole body. It also escalated his lower moans to high pitched messes.

“I’m gunna fill you up Blackbird.” Night spasmed around him, keening while his legs collapsed. Cross’s strong arms picked him up and rocked into him one, two, three times, powerful and rough before letting go himself.

Nightmare could only lean back shivering against Cross’s chest, eye closed to the mirror and the outside world, the only feeling being the warm ribbons of cum shooting into him from Cross and a deep sense of completion. He’d started to shiver from the cold before Cross’s arms wrapped around him. Endless clanks anywhere his love could reach, Cross lived for the afterglow.

“You feel so good.” Nightmare hummed in response, hand drifting over his cyan belly, still warm from their actions. He opened his eye. 

_ Oh _ .

The mirror gave him the full picture, naked and tangled up with Cross, a burst of purple magic pooled inside his waist. He rubbed over the comfortably full ecto.

“You really enjoyed it this time.” Cross watched him from over his shoulder, eyes fond as he watched Night tend to remnants of their union. “It’s good we had a safe word. I was worried you’d slipped into something bad for a second there.” Night leaned back to kiss him properly.

“I know I’m safe with you.” He puffed up with the praise, always worried about the trust he knew Night had given him far too easily, grateful starbursts of positivity radiating off him. 

“That’s good. I’m glad.” Cross drifted down to hold Night’s hand against his stomach. “Are you sure it’s ok to do this? The first time was an accident, and you apparently really like it, but aren’t you worried about soulings or something?” Cross could feel the involuntary squeeze at the mention.

“I don’t know if my corrupted form can carry, but I’m not worried regardless.” Nightmare kissed over the scar on his cheek, his favorite. “And I prefer it because the...others...never did. They didn’t want to risk that with me.” He could feel Cross’s anger from here, riled up for his sake, which he sapped away through the touch of his tendrils still wrapped around Cross. “Feeling this helps me remember things are different now.”

“Then I don’t mind.” Cross cuddled them together. The larger implications were left alone, something to be discussed over more than pillow talk. He circled around to a topic he revisited most nights with Cross.

“You know, we can try to work up to something more possessive if you want. I can tell you want to and we have a safe word.”

“I don’t need it. I’d rather have you.” Cross shook his head vehemently. Nightmare sighed, then dropped it. It’d only be a pointless talk today and Night wanted to soak in more of the positive vibes. He DID want to chat though, so he switched to something else to distract Cross.

“So I’m Blackbird now?” Cross tried to hide his face, but the mirror gave him away. Nightmare still found that blush adorable even now.

“Maybe. You’re very cute and have a nice voice.” Cross gave up hiding to meet Night’s gaze head-on, making Night flush cyan too, both an embarrassed mess in front of the other. “Would you object, Blackbird?”

“I’ve never been called that before.” He let Cross read between the lines.

“My Blackbird. I like it.” His softened member slipped out, but they still relaxed together. Cross’s default seemed to be kissing along his collarbone absentmindedly, which when left unchecked, escalated to nibbles, which Night already felt the first one on the left near his arm. Night hummed into it.

“Me too.” Those crafty hands had already started to place themselves in more compromising positions. He gasped when they brushed up against his still summoned chest. “Cross.”

“Can’t help it.” Cross murmured into his ear. “I told you, you’re cute.” He nodded towards the mirror. Nightmare rolled his eyes, but his body was reacting, already loosened and craving more. He spun around in Cross’s lap to face him, pulling him into a passionate kiss, tongues tangled and needy. When they broke apart, Nightmare took Cross’s hands and placed them on his hips.

“I suppose since I’m your Blackbird, let me sing for you.”

**Author's Note:**

> This is Top Cross 2021!


End file.
